I am suffering from extreme brightness on Ubuntu 18.04. I have recently downloaded this version, however my brightness keys are not working and I cannot change the brightness levels. My PC is Lenovo Yoga S740.
xrandr is not working I have tried it before. It gives me this error:
xrandr: Failed to get size of gamma for output default
Also this does not give any output:
I have also tried to change the grub file but nothing is working for me. (I also tried to change it as acpi_backlight=video etc.)
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
Finally, xbacklight doesn't work too. How can I solve this issue?